Tanning assisted by basic aluminum chloride and nitrates complexed with dicarboxylic acids or aromatic hydroxy carboxylic acids



United States Patent TANNlNG ASSISTED BY BASIC ALUMINUM CHLO- RIDE AND NITRATES COMPLEXED WITH DI- CARBOXYLIC ACIDS 0R AROMATIC HYDROXY CARBOXYLIC ACIDS Rudi Heyden and .l'urgen Plapper, Dusseldorf, Germany, assignors to Bohme Fettchemie G.m.b.I-I., Dusseldorf, Germany, a corporation of Germany No Drawing. Griginal application Jan. 19, 1960, Ser. No. 3,247. Divided and this application Apr. 24, 1963, Ser. No. 279,351

6 Claims. (Cl. 8-94.24)

This application is a division of our application Serial No. 3,247.

This invention relates to the production of water soluble, aluminum-containing complex salts and to a process and bath for treating leather with such salts.

We have found that these water-soluble, organic aluminum-containing complex salts can be obtained 'by a reaction of basic salts of aluminum which are dissolved in low molecular alcohols with alcoholic solutions of lower or medium molecular carboxylic acids.

Judging from the chemical behavior of these complex salts, the organic carboxylic acid radicals are apparently combined with the aluminum into a cation which in turn is combined with the anion of the basic aluminum salt used as the starting material to form a salt-like compound. Accordingly, the reactions of aqueous solutions of this complex are different from the normal aluminum salts. For example, the complex cation often combines with sulfate ions into an insoluble or difiicultly soluble salt and, after addition of an excess, does not redissolve. The oxalates, carbonates and chromates are also diflicultly soluble. In addition, precipitates are obtained with aqueous solutions of salts of olymeric organic acids, such as with polyphosphates or phosphorus tungstenates, and solutions of resin acids or their salts also have a precipitating effect upon the aluminum complexes.

We have found that these aluminum complex salts are extraordinarily suitable as auxiliary tanning agents to achieve special effects in combination with vegetable, synthetic or resin tanning agents as well as chrome and fatty tanning agents. In general, it is possible to achieve therewith a greater fullness, a distinctly finer and more solid grain structure as well as good buffing properties. Vegetable-tanned leather can be dyed more uniformly and more completely after treatment with such auxilliary agents. In modern, soft, chrome tanned uppers, which often have a loose grain, it is possible to achieve an improvement in the grain strength by an additional tanning step with these auxilliary agents.

It is an object of this invention to produce water soluble, aluminum-containing complex salts by a reaction between basic salts of aluminum and carboxylic acids.

A further object is to produce a compound which is useful as a tanning assistant to improve the fullness and grain structure of leather tanned with vegetable, synthetic, resin, chrome and fatty tanning agents.

Another object is to provide a method and bath for treating leather in conjunction with a conventional tanning process to obtain improved fullness, grain structure and buffing properties.

These and other objects of our invention will become apparent as the description thereof proceeds.

Suitable basic salts of aluminum for our process are primarily the basic chlorides and nitrates, as well as other basic aluminum salts which are soluble in alcohols. The basicity may vary within wide limits, that is 33% as well as 66% basic salts may be used. The basicity may, however, also he above or below these values.

3,232,696 Patented Feb. I, 1966 Suitable carboxylic acids are low molecular or medium molecular aliphatic, cycloaliphatic as well as aromatic monoand polycarboxylic acids for example aliphatic monoor polycarboxylic acids, such as fatty acids, naphthenic acids, oxalic acid, adipic acid, sebacic acid, benzoic acid, phthalic acids, melitic acid, naphthalene carboxylic acids, and the like, or also unsaturated aliphatic carboxylic acids, such as acrylic acid, methacrylic acid, crotonic acid, sorbic acid, maleic acid, fumaric acid and the like. In addition to the carboxyl groups, these acids may also carry other substituents such as hydroxyl, cyano and mercapto groups or also halogen substituents. The prerequisite is that these substituents do not react with the basic aluminum salts. Suitable low molecular monovalents alcohols which may 'be used as solvents in this process are, for example, methanol, ethanol, isopropanol, tetrahydrofurfuyl alcohol and the like. The alcohols do not only serve as solvents, but are apparently also built into the complexes.

If the complex salts obtained by the process described above are completely freed from residual solvent in vacuo they lose their water-solubility. However, the water-solubility may often again be restored if the products are admixed with small amounts of alcohol. Thereafter, they are again completely water-soluble.

It is known to produce water-soluble chrome complex salts from basic chromium salts and aromatic carboxylic acids. In view of the considerably lower capability of aluminum to form complex compounds, the formation of aluminum complexes under the describe-d conditions is surprising. In comparison to the chromium complex salts, the colorlessness of the aluminum complex salts represents a considerable advance for technical use. In addition, basic aluminum salts have previously been transformed with high molecular fatty acids into complex compounds but the products obtained thereby did not form clear solutions. Thus, the present process represents a distinct ad vance over the known state of the art.

The following specific examples are set forth to illustrate our invention and to enable persons skilled in the art to better understand and practice the invention and it will be understood that the invention is not limited thereto.

Example I 120 parts by weight aluminum isopropylate were dissolved in 300 parts by weight isopropanol. To this solu tion a mixture of 60 parts by weight concentrated aqueous hydrochloric acid and 60 parts by weight isopropanol was added. A 66% basic aluminum chloride solution was immediately obtained. The preparation of the basic aluminum chloride solution may also be carried out with the aid of aluminum chloride hexahydrate which is dissolved in an alcohol, such as methanol, is then transformed into the basic salt by addition of alcoholic sodium hydroxide.

parts by weight of this aluminum chloride solution were admixed at elevated temperatures and while stirring with a solution of 125 parts by weight of octyl adipic acid, obtained by hydrogenation and subsequent oxidation with nitric acid of p-octyl phenol, and the resulting mixture was heated at the boiling point for 4 hours. A clear solution was obtained which is dilutable with water and produced an insoluble precipitate with ammonium sulfate.

For the preparation of a corresponding complex, dodecyl malonic acid may be used in equimolar amounts in the same amounts as octyladipic acid.

Example 11 90 parts by weight of the basic aluminum chloride solution obtained in Example I were admixed at elevated temperatures and accompanied by stirring with 18.9 parts by weight butane-1,2,4-tricarboxylic acid in parts by .ture was boiled for 3 hours. -tained which was miscible with water in any desired ratio.

weight isopropanol, and the resulting mixture was heated for 3 hours. A clear highly viscous solution was obtained. An equal amount of isopropanol was added to this solution, whereby a product was obtained which was dilutable with water in any desired ratio and formed a clear aqueous solution.

Example III 90 parts by weight of the 66% basic aluminum chloride solution obtained in Example I, were admixed with a solution of 16.6 parts by weight orthophthalic acid in 120 parts by Weight isopropanol, and the resulting mixture was boiled for 3 hours while stirring. A complex salt solution was obtained which was miscible with water in any ratio and formed a clear solution.

Example IV 69 parts by weight salicylic acid were admixed with 62.5 parts by weight water, 2.5 parts by weight sulfuric :acid and 27.5 parts by weightot a 30% aqueous solution of formaldehyde and the resulting mixture was heated at 95 C. for 5 hours. At the end of this time the aqueous solution collected above the resin formed by the reaction was decanted and the resin was Washed several times with water. The 95 parts by weight of resin thus obtained were dissolved in 250 parts by weight hot isopropanol.

345 parts by weight of this resin solution were admixed with 885 parts by weight of the 66% basic aluminum salt solution obtained in Example I, and the resulting mix- A clear solution was ob- Example V 98 parts by weight of the 66% basic aluminum chloride solution were admixed with a solution of 12.5 parts by weight octyl salicylic acid in 50 parts by weight isopropa- 1101 while stirring, and the resulting mixture was heated at the boiling point for 3 hours. A clear solution was obtained which was dilutable with water in any desired ratio.

These and aluminum carboxylic acid complex com- .pounds of similar structure may be usedas auxilliary tanning agents, for example, in the folowing manner.

Example VI Chrome-tanned, neutralized cow hide uppers were treated with to 20% of the solution described in EX- ample IV and 100% water for 2 hours. Thereafter, the leather was fat-liquored with 3% of a customary fatliquoring agent mixture and then finished in normal manner. A full, firm-grained upper leather with good 'bufiing properties was obtained.

Example VII Chrome-tanned upper leather which had been retanned with resin or vegetable-synthetic tanning agents were treated for 30 minutes in the same bath with 10% of the solution described in Example IV and were then fat liquored in the customary manner. Fine, firm-grained, full, combination tanned upper leather with good buifing properties was obtained.

Example VIII Bated, shaved calf hides were pretanned with 5 to of the solution described in Example IV in 100% solution for 1 to 2 hours and were then transferred to another bath where they were tanned with about of a vegetablesynthetic tanning agent mixture. The leather was fatliquored in the usual manner. Calf uppers with a shrivel elTect were obtained.

Example IX Chrome tanned cow hide uppers were retanned with commercial resin tanning agents and were then treated in the retaining bath for 30 minutes with 10 to 20% of a solution corresponding to that described in Example IV.

A full, firm-grained upper leather was obtained which had particularly good and uniform dyeing properties.

While we have set forth specific examples and preferred modes of practice of our invention, it will be understood that these are for the purpose of illustration, and that various changes and modifications may be made in our invention without departing from the spirit of the disclosure or the scope of the appended claims.

We claim:

I. A process for tanning animal hides which comprises contacting said hides sequentially with a tanning agent and an aluminum carboxylic acid complex salt produced by reacting a solution of basic aluminum chloride in isopropanol with a solution of a resinous compound produced by reacting salicylic acid, sulfonic acid and formaldehyde and dissolving said resin in isopropanol.

2. A process for tanning animal hides which comprises contacting said hides sequentially with a chrome tanning agent and an aluminum carboxylic acid complex salt produced by reacting a solution of basic aluminum chloride in isopropanol with a solution of a resinous compound produced by reacting salicylic acid, sulfuric acid and formaldehyde and dissolving said resin in isopropanol.

3. A process for tanning animal hides which comprises contacting said hides sequentially with a resin tanning agent and an aluminum carboxylic acid complex salt produced by reacting a solution of basic aluminum chloride in isopropanol with a solution of a resinous compound produced by reacting salicylic acid, sulfuric acid and formaldehyde and dissolving said resin in isopropanol.

4. A process for tanning animal hides which comprises contacting said hides sequentially with a vegetable tanning agent and an aluminum carboxylic acid complex salt produced by reacting a solution of basic aluminum chloride in isopropanol with a solution of a resinous compound produced by reacting salicylic acid, sulfuric acid and formaldehyde and dissolving said resin is isopropanol.

5. A process for tanning animal hides which comprises contacting said hides sequentially with a synthetic tanning agent and an aluminum carboxylic acid complex salt produced by reacting a solution of basic aluminum chloride in isopropanol with a solution of a resinous compound produced by reacting salicylic acid, sulfuric acid and formaldehyde and dissolving said resin in isopropanol.

6. Process :for tanning animal hides by successive treatment with a tanning agent and a water-soluble organic aluminum complex salt which is obtained by reaction of a solution of a basic aluminum salt, said salt being selected from the group consisting of chlorides and nitrates, in low molecular weight alcohols with solutions of carboxylic acids selected from the group consisting of aliphatic, cycloaliphatic and aromatic carboxylic acids with at least two carboXyl groups, and aromatic carboxylic acids having at least one carboxyl group and one hydroxyl group, in low molecular weight alcohols.

References Cited by the Examiner UNITED STATES PATENTS 1,891,440 12/1932 Nolan 8-94.29 2,301 ,637 11/1942 Neidercorn 894.29 2,823,144 2/1958 Dalton. 2,847,396 8/1958 Sellet 894.29

FOREIGN PATENTS 333,221 1930 Great Britain. 768,762 2/ 1957 Great Britain.

OTHER REFERENCES Martin: The Chemistry of Phenolic Resins, page 54, pub. 1956 by John Wiley & Sons, Inc.

NORMAN G. TORCHIN, Primary Examiner.

A. LOUIS MONACELL, Examiner. 

6. PROCESS FOR TANNING ANIMAL HIDES BY SUCCESSIVE TREATMENT WITH A TANNING AGENT AND A WATER-SOLUBLE ORGANIC ALUMINUM COMPLEX SALT WHICH IS OBTAINED BY REACTION OF A SOLUTION OF A BASIC ALUMINUM SALT, SAID SALT BEING SELECTED FROM THE GROUP CONSISTING OF CHLORIDES AND NITRATES, IN LOW MOLECULAR WEIGHT ALCOHOLS WITH SOLUTIONS OF CARBOXYLIC ACIDS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC, CYCLOALIPHATIC AND AROMATIC CARBOXYLIC ACIDS WITH AT LEAST TWO CARBOXYL GROUPS, AND AROMATIC CARBOXYLIC ACIDS HAVING AT LEAST ONE CARBOXYL GROUP AND ONE HYDROXYL GROUP, IN LOW MOLECULAR WEIGHT ALCOHOLS. 